linux-kernel - Re: [PATCH 4/5] mm, memcg: avoid possible NULL pointer dereferencing in mem_cgroup

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Date:   Fri, 30 Jul 2021 09:50:13 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     <hannes@...xchg.org>, <mhocko@...nel.org>,
        <vdavydov.dev@...il.com>, <akpm@...ux-foundation.org>,
        <shakeelb@...gle.com>, <guro@...com>, <alexs@...nel.org>,
        <richard.weiyang@...il.com>, <songmuchun@...edance.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <cgroups@...r.kernel.org>
Subject: Re: [PATCH 4/5] mm, memcg: avoid possible NULL pointer dereferencing
 in mem_cgroup_init()

On 2021/7/29 21:52, Matthew Wilcox wrote:
> On Thu, Jul 29, 2021 at 08:57:54PM +0800, Miaohe Lin wrote:
>> rtpn might be NULL in very rare case. We have better to check it before
>> dereferencing it. Since memcg can live with NULL rb_tree_per_node in
>> soft_limit_tree, warn this case and continue.
> 
> Why would we need to warn?  the GFP flags don't contain NOWARN, so
> we already know an allocation failed.

I see. Will remove it. Many thanks!

> .
>